I would go for a British manufactured webley long bar actioned (pre-war) DR. There is an excellent Army Navy 470NE on gun broker right now, and the reserve is around $20k

I have also seen some Rigby's around for $22k-$24k

Given the fact you have never hunted a "tusker" before I would assume that your PH will have you at a safe distance in which case a 470 will do the job best.

Also take resale in to account, as this is a major investment and not just a mear tool in your case. You will want to get your money out of it, and it may even appreciate a bit in your short time with it being the most popular calibre overall.

Stay (pre-war) the market is always more adapt to those DR's for higher resale. Stay away from new Merkel stuff, its not even comparable in this case.

Bye your gun this year, shoot it and get used to it.

Next year book your hunt for September if going to Africa, and in the meantime read "in the salt" by Lou Hallamore.